The present invention relates to printing inks containing a liquid hydrocarbon solution of a limed resinous binder wherein said binder comprises the reaction product of calcium hydroxide and rosins wich a polyanhydride of an .alpha.-olefin-maleic anhydride. The invention relates also to the method of making the ink vehicles.
Limed rosin is widely used in inks, coatings, etc., and is prepared by the fusion method or the solution method. The solution method is very desirable when the limed resinate can be made in a solvent that is useful in the ink or coating that is to be prepared. In coatings and inks using hydrocarbons as solvent, it is necessary that the limed rosin be soluble in the commonly used hydrocarbon solvent. In the past it has been impossible to prepare limed rosins, especially limed tall oil rosin, or mixtures of rosin which include tall oil rosin, that are soluble in hydrocarbons when the degree of liming is more than about two-thirds of the amount of lime required to form the di-resinate. Rosin consists predominantly of resinous monocarboxylic acids with only a minor amount of non-acidic material. Tall oil rosin differs from wood and gum rosins in that it contains 2-3% of fatty acids. The rosin acids are monocarboxylic acids of alkyl hydrophenanthrene, e.g. abietic acid. In the liming process the monocarboxylic acids of rosin react with calcium hydroxide to form calcium salts, or resinates. Theoretically, the resinous acids can react to form either calcium di-resinate or basic calcium mono-resinate, i.e., Ca' (resinate) or CA (OH) (resinate). The calcium di-resinate contains approximately 6.2% calcium while the basic calcium monoresinate contains 11.2% calcium. In accordance with prior art processes, it is not possible to incorporate more than about 6 to 7 parts of calcium hydroxide per 100 parts of rosin in a solution liming of rosin, especially tall oil rosin. Assuming complete conversion of lime to di-resinate, this would give a product containing 3.06 to 3.56 calcium. As the percentage of calcium increases, the melting point of the resinate increases, and this is important in the printing ink field, and results in it being desirable to increase the degree of liming in order to obtain the more desirable higher melting resinates. Therefore, there is a need and a desire in the industry to have a solution method for making high melting calcium resinates that are soluble in hydrocarbon solvents commonly used in printing inks and coatings.
In co-pending application Ser. No. 947,146 filed Sept. 29, 1978 entitled Calcium Resinates and Inks, limed resinates and printing inks containing the limed resinates are disclosed. The application describes the preparation of a rosin preferably limed in solution in a hydrocarbon solvent in the presence of a polymeric polycarboxylic acid wherein the polymeric polycarboxylic acid is a partial ester of a 1.3:1 molar ratio copolymer of maleic anhydride and .alpha.-olefin.